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Lesson 4: Helm Charts

Introduction

Helm is a package manager for Kubernetes that provides a convenient way to share and install community applications. By packaging manifests into reusable 'Charts', complex projects can be installed with a single command, including any dependencies. Helm handles versioning and allows customisation through templatable values.

In this lesson, we'll deploy a community application available as a Helm chart to our minikube cluster.

⚠️ Security

Like all code on the internet, Helm charts can contain malicious content. Only install Helm charts from trusted sources. Vetting charts using Helm's template and verify commands and other best practices are discussed in the sysdig article in Further Reading.

Prerequisites

On Linux/WSL, Helm can be installed as a snap package

sudo snap install helm --classic

On macOS, it is available through Homebrew

brew install helm

Other Windows users can use the Chocolately package manager:

choco install kubernetes-helm

You can verify your installation by running helm version.

🍹 Deploying Mocktail with Helm

Mocktail is a minimalist server that allows you to define and test custom API endpoints. We'll use it to demonstrate deploying a collection of kubernetes manifests to our cluster using a Helm chart.

Understanding Helm Repositories

Helm Charts can be found in two main ways:

  • On community repositories like Artifact Hub, with many projects
  • On individual repositories e.g. on GitHub for specific projects

Mocktail provides its own Helm repository, which we can add to Helm with

helm repo add hhaluk https://huseyinnurbaki.github.io/charts/

It's a good idea to periodically get Helm to check for updates from added repositories: 

helm repo update

Deploying Mocktail

Having added the Mocktail helm repository, the application can be deployed to our minikube cluster with

helm install mocktail hhaluk/mocktail -n mocktail --create-namespace

That's it! In the background, Helm organised:

  • Downloading the chart and generating all necessary manifests
  • Creating a namespace for the manifests to be deployed to
  • Creating deployments and services
  • Starting the application

Access Monktail

Query the service

minikube service mocktail-svc --url -n mocktail

The URL should take you to the Mocktail dashboard.

Optional: Test the Mock API

Try creating a custom endpoint in the dashboard:

  1. Add a new GET endpoint: /surprise
  2. Set the response:
{
      "message": "Hello from Kubernetes!",
      "pod": "mocktail-pod",
      "surprise": "🎲"
}

    3. Test it with curl from a Terminal:

curl <mocktail-dashboard-url:PORT>/mocktail/surprise

💡 The jq command can be used to pretty-print the JSON returned by the request: curl .../surprise | jq

Customising Charts with Values

A powerful feature of Helm is the ability to customise applications with your own parameters. First, view available configuration options for Mocktail:

helm show values hhaluk/mocktail

Let's override the default replicaCount: 1 to have three replicas for the service. This can be done using the --set OPTION=VALUE syntax for the install/upgrade command:

helm upgrade mocktail hhaluk/mocktail --set replicaCount=3 -n mocktail

For larger number of changes, you can write a custom-values.yaml file and apply them with helm. We have provided a file at helm/custom-values.yaml for updating the existing helm release with an ingress. 

helm upgrade -i my-mocktail hhaluk/mocktail -n my-mocktail --create-namespace -f helm/custom-values.yaml

The above command can be used for a first time install of a helm release or to upgrade an existing release due to the -i flag.

This upgrade has changed the container port that the service listens on.

There are a large number of community charts covering thousands of web and infrastructure projects. Charts on Artifact Hub may be searched directly from the command line with

helm search hub <search-term>

You can also search in any repositories you have added. For example, first adding the popular Bitnami Library:

helm repo add bitnami https://charts.bitnami.com/bitnami
helm repo update

Then

helm search repo <search-term>

(Optional) Cleaning up helm charts

Helm comes with a handy process to also remove resources that have been added to the cluster. We can clean up everything we deployed during this lession using: 

helm uninstall mocktail -n mocktail
helm uninstall my-mocktail -n my-mocktail

You can check that the resources have been removed by using kubectl or checking for the helm releases:

helm list -n mocktail
helm list -n my-mocktail

Note: This will not remove the namespace itself for that you need to separately run `kubectl delete namespace mocktail my-mocktail

📚 Further Reading